Data presented at the American Heart Association meeting in New Orleans …

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There is bad news for patients with pacemakers who like listening to music on their iPods. According to data presented at the current American Heart Association meeting in New Orleans, personal music devices such as iPods might not represent a risk to patients with implanted pacemakers or defibrillators, but the headphones used to listen to those devices might.

At issue are the magnets that drive the little speakers in the headphones. Implanted pacemakers and defibrillators are rather sensitive to magnetic fields, and clinicians use magnets to calibrate and test the devices under controlled conditions. After measuring the magnetic field strength of eight different brands of MP3 player headphones, researchers at Beth Israel Medical Center in Boston discovered that all of them were an order of magnitude stronger than needed to influence an implanted pacemaker of defibrillator.

They then confirmed this effect by testing it with patients, where they found that 15 percent of the pacemaker patients and 30 percent of the defibrillator patients carried devices that responded to the magnets.

Luckily, the problem doesn't occur when the headphones are used to actually listen to music, as the distance between the ears and the implanted device is too great. However, if the headphones are closer than 3 cm to the skin around the heart, the potential for interference is there.

This might not seem such a massive deal but, since the magnets cause this effect regardless of whether the device is on or even plugged in, it means that a patient who had their headphones draped over their neck or in a breast pocket could be at risk. Dr. Willam Maisel, lead author of the study, cautions patients that, regardless of the brand, they should always ensure that their headphones remain at least 3 cm (1.5 inches) away from the site of their devices.